1. Field of the Invention
The present invention relates generally to a weight trainer's unit construction, and more particularly to an innovative one which is configured with a counterweight module.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
The weight trainer, an important piece of fitness equipment, is structurally designed in such a way to bear load and adjust the balance weight, enabling the users to exercise their muscles on arms and legs, etc.
The structural configuration of counterweight module is crucial to the weight trainer, since the convenience of its weight adjustment and stability of movement are closely related to the applicability and quality of the weight trainer. Hence, continuous efforts are made in this industry to develop more applicable models.
Generally, the counterweight module of the weight trainer is constructed in such a manner that the training weight is increased by means of serial stacking. Yet, it is found in actual applications that, the weight of the counterweight blocks can be adjusted by stacking from bottom to top, or removing from top to bottom, leading to time-consuming and inefficient selection and change of weight. For this reason, a counterweight module disclosed in FIG. 1 has been developed, i.e. several counterweight blocks 10 of equivalent width are superimposed along two vertical guide rods 11. Vertical through-holes 12 are set correspondingly at the middle of the counterweight blocks 10 for penetration of a lifting column 13. A pivoted locating hole 14 is set on the lifting column 13 correspondingly to the counterweight block 10 for selective bolting of pin 15, allowing to quickly switch the intended counterweight blocks 10. Moreover, two sleeving holes 16 are arranged at interval onto every counterweight block 10 for sleeving onto two vertical guide rods 11. As the counterweight block 10 is made of rough cast iron, filled sand or covered iron material under plastic surface, a colloid liner ring 17 is assembled into the sleeving hole 16 of every counterweight block 10, permitting to sleeve out of vertical guide rod 11 at a micro-clearance, realizing smooth sliding between the counterweight block 10 and the vertical guide rod 11. Besides, the vertical through-holes at middle of the top counterweight block are mated with the lifting column by means of welding and tight fit. However, the following shortcomings are still found despite of the existing advantages of the prior art:
As the colloid liner ring 17 assembled into the sleeving hole 16 of every counterweight block 10 is sleeved out of the vertical guide rod 11 at a micro-clearance, the friction factor at a cylindrical contact area will be generated between the colloid liner ring 17 of every counterweight block 10 and the vertical guide rod 11. With the increasing number of the counterweight blocks 10, the frictional resistance will grow with the lifting action, leading to loss of the accuracy of weight adjustment. This is because the friction factor between the colloid liner ring 17 of the counterweight block and the vertical guide rod 11 will generate a damping phenomenon during lifting motion of the counterweight blocks 10. In such cases, the actual load borne by the users is much bigger than the weight of the counterweight blocks 10. When the force applied by the user is released, the falling resilience of the counterweight blocks 10 will become stagnant due to the friction factor, leading to loss of the accuracy.